1. Field of the Invention
The present invention relates to a spread spectrum signal estimator and more specifically to one which interfaces with a spread spectrum modem and adaptive array processor in such a way that the adaptive array can null interfering signals, but not the desired signals.
2. Description of the Prior Art
The basic attempt at signal null inhibition for adaptive arrays appeared in the technical article entitled "Adaptive Antenna Systems", B. Widrow, et al., Proceedings of the IEEE, Vol. 55, No. 12, Dec. 1967, pp. 2143-2159. Widrow's system required a knowledge of the direction of signal incidence and did not address the pseudo noise (PN) type of received signal.
A PN type of estimator has been disclosed by R. T. Compton et al., in a technical article entitled "Adaptive Arrays For Communication Array Systems: An Overview of Research at the Ohio State University", appearing in the IEEE Transactions on Antennas and Propagation, Vol. AP-24, No. 5, Sept. 1976, and in "Adaptive Antennas for Speed Spectrum Communication Systems", D. C. Upp et al., Ohio State University, Interim Technical Report 3098-3, Oct. 1972, Contract N00014-67-A-0232-0009, AD 754444. These publications disclose an estimator that is quite complex and has the ability to handle one signal only, i.e., no conferencing capability. It uses a delay lock tracking loop for synchronization and as stated in D. C. Upp's report "although this type of synchronization is acceptable for laboratory purposes, it would not be suitable for acquisition in a real communication system".